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MCQs: Normal Probability

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Find the area under the standard normal curve between z=0 and z=3.

A. 0.4987
B. 0.9987
C. 0.4641
D. 0.0010

IQ test scores are normally distributed with a mean of 100 and a standard deviation of 15. An individual's IQ score is found to be 110. Find the z-score corresponding to this value.

A. -1.33
B. 1.33
C. -0.67
D. 0.67

The lengths of pregnancies of humans are normally distributed with a mean of 268 days and a standard deviation of 15 days. A baby is premature if it is born three weeks early. What percentage of babies are born prematurely?

A. 9.21%
B. 8.08%
C. 6.81%
D. 10.31%

The distribution of cholesterol levels in teenage boys is approximately normal with and (Source: U.S. National Center for Health Statistics). Levels above 200 warrant attention. Find the probability that a teenage boy has a cholesterol level greater than 225.

A 0.0718
B 0.0012
C 0.0336
D 0.0606

An airline knows from experience that the distribution of the number of suitcases that get lost each week on a certain route is approximately normal with ? = 15.5 and Ï? = 3.6. What is the probability that during a given week the airline will lose less than 20 suitcases?

A 0.4040
B 0.3944
C 0.1056
D 0.8944

Assume that blood pressure readings are normally distributed with and A blood pressure reading of 145 or more may require medical attention. What percentage of people have a blood pressure reading greater than 145?

A. 99.91%
B. 6.06%
C. 0.09%
D. 11.09%

Assume that the salaries of elementary school teachers in the United States are normally distributed with a mean of $32,000 and a standard deviation of $3000. If a teacher is selected at random, find the probability that he or she makes more than $36,000.

A. 0.1056
B. 0.0918
C. 0.4040
D. 0.9082

IQ test scores are normally distributed with a mean of 100 and a standard deviation of 15. Find the x-score that corresponds to a z-score of -1.645.

A. 79.1
B. 91.0
C. 82.3
D. 75.3

For the standard normal curve, find the z-score that corresponds to the 90th percentile.

A. 0.28
B 1.52
C 1.28
D 2.81

Find the z-scores for which 90% of the distribution's area lies between -z and z.

A.(-0.99,0.99)
B.(-1.645,1.645)
C.(-2.33,2.33)
D.(-1.96,1,96)

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Solution Summary

The solution provides answers to multiple choice questions on normal probability. Relevant workings are also included.

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See Also This Related BrainMass Solution

Normal Probability

12. Find the area under the normal distribution curve to the right of z = -3.24. (Points : 1)
0.499
-0.499
0.999
0.001

13. Use a scatter plot to deternine the relationship between the x values and the y values.
(Points : 1)
No relationship
Nonlinear relationship
Positive linear relationship
Negative linear relationship

14. The average hourly wage of employees of a certain company is $9.83. Assume the variable is normally distributed. If the standard deviation is $4.58, find the probability that a randomly selected employee earns less than $5.43. (Points : 1)
0.313 = 31.3%

0.332 = 33.2%

0.168 = 16.8%

0.345 = 34.5%

15. Find the area under the normal distribution curve between z = -1.34 and z = 2.95. (Points : 1)
0.908
0.088
0.410
0.498

16. Find the equation of the regression line.
(Points : 1)
y = -1.2 + 2.4x
y = 1.2 + 2.4x
y = 2.4 + 1.2x
y = -2.4 + 1.2x

18. Determine whether a correlation coefficient of r = -0.405 is significant at the 5% level for a sample size of 22. (Points : 1)
r is not significant at 5%.
r is significant at 5%.

19. Find the area under the normal distribution curve between z = 1.52 and z = 2.43. (Points : 1)
0.929
0.436
0.493
0.057

6. Use the equation of the regression line to predict y when x = 20.
(Points : 1)
45.5
50
40
48.5

7. Find the area under the normal distribution curve to the right of z = -1.03. (Points : 1)
0.151
-0.349
0.349
0.849

9. Find the value for the correlation coefficient r.
(Points : 1)
-0.073
-0.094
-0.203
-0.149

10. A data set of size 19 has correlation coefficient of r = -0.432. Test the significance of r at the 5% level and at the 1% level. (Points : 1)
r is significant at 5% and at 1%.
r is significant at 5%, but not at 1%.
r is is not significant at 5% or at 1%.

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